Study Of Compact TE₀₁-mode Converter With High Efficiency

The circular electric TE₀₁ mode is generated and applied to gyrotron devices,and its far-field radiated power is funnel-shaped,which is unfit to be applied directly.HE₁₁ mode,which has a quasi-Gaussian field distribution,is suitable to be directly employed.Thus,a special mode converter is usually needed to transform TE₀₁1 mode into HE₁₁1 mode.After the TE₀₁-TE₁₁-HE₁₁ mode converter is designed,the input end of the converter must be excited by a low-power and high-efficiency TE₀₁ mode in order to understand and verify the performances of the above converter.Considering that the output mode of the conventional microwave power source is not the TE₀₁ mode,a TE₀₁-mode converter needs to be designed to convert the output mode into the TE₀₁ mode.In order to ensure the credibility of the test results,a TE₀₁-mode converter which outputs mode purity as high as possible is very much needed.In additional,in order to meet the requirement of the compactness and small structure of the test system,the mode converter is also required to be as compact as possible.Therefore,it is of great significance to study the TE₀₁-mode converter with high mode purity,high conversion efficiency and compactness.The main works and research results reflected in this paper are as follows:1.Research on rectangular TE₁₀0 mode-rectangular TE₂₀0 mode converter.Based on the distribution of the electromagnetic field,this paper summarizes a distribution of the electric field at the cross section,that is,the shortest path distribution characteristics?SPDC?,which is proposed in this paper.Using this characteristics,an improved T-junction TE₁₀-TE₂₀ mode converter is designed.The simulation results show that the converter has a good agreement with the theoretical prediction,and proves the feasibility of the SPDC of the electric field.2.Research on rectangular TE₂₀ mode-circular TE₀₁ mode converter.Based on the theory of stepped waveguide coupled wave and multi-step wideband matching transmission,a new type of rectangular TE₂₀ mode to circular TE₀₁ mode converter,which is also called a stepped thigh-bone-type mode converter,is designed using SPDC of the electric field.The simulation results reveal that SPDC can be applied to design the converter with compactness,broadband,high conversion efficiency and high purity.3.Research on the inline-type circular TE₀₁-mode converter.A new inline-type TE₁₀-TE₀₁mode converter operating in Ka-band is formed by splicing a T-junction TE₁₀-TE₂₀ mode converter and a thigh-bone-type mode converter.The simulated results show a mode purity higher than 98%with an energy conversion efficiency of nearly 96%from 32.28 GHz to37.54 GHz,which its relative bandwidth is 15.2%,and the total length is less than 6?.The experimental results are in good agreement with the corresponding simulation results,which indicates that the designed converter has the performances of compactness,broadband,high conversion efficiency and high mode purity.4.Research on the sidewall-type circular TE₀₁-mode converter.In order to further improve the mode purity,a stepped coaxial six-power sidewall-coupled mode converter is presented based on the theory of sidewall coupling and Y-branch.The simulation results indicate that the designed converter achieves a mode purity greater than 99.8%with a conversion efficiency of nearly 96%within the frequency band of 29.9 GHz to 32.8 GHz and that its relative bandwidth is up to 9.25%.It shows that the designed TE₀₁-mode converter has the advantages of higher mode purity.